Heavy corrugated plastic is a sturdy, durable material that is useful for making many products. Among those products are containers, trays, boxes and other walled receptacles.
Such structures are usually made by cutting an appropriate shape from a heavy corrugated plastic sheet, and then bending portions of the sheet to form walls. The sheets of material are prepared for bending by having applied to them, under some pressure, dies that compress the material enough to allow it to be bent. Corners are made by connecting overlapping surfaces of the bent portions with adhesive or ultrasonic welding.
This procedure requires setting up die rules fixed in a wood platform, since the pressure required means that the die rules must be securely fixed in a press. Even so, the pressure from fixed die rules is usually not enough to adequately score for bending corrugated plastic of more than 5 millimeters of thickness. The bending process does not eliminate the memory of the thermoplastic, as it wants to return back to a flat sheet. The additional step of securing corners by adhesives or ultrasonic welding is time-consuming and expensive. Furthermore, the boxes so constructed have bends that are so difficult to maintain in that the folded walls tend to bow out so that reinforcing steel wires are needed to maintain the shape of the receptacle.
It is an object of this invention to provide an improved method and apparatus for forming walled receptacles from heavy corrugated plastic sheets.